This is a research program in the broad area of cardiopulmonary pathophysiology. Specific topics of investigation range from predominantly cardiovascular to predominantly pulmonary but are related through similar experimental and mathematical techniques. Individual subprograms include: "Coronary Circulation in Normal and Abnormal States"; "Mechanisms of Arrhythmia Production"; "Kinetics of Gas Exchange in the Lungs and Tissues"; "Intrapulmonary Distribution of Ventilation and Perfusion in Normal and Abnormal States"; "Cardiopulmonary Flow Models"; and "Methodological Techniques for the Evaluation of Cardiopulmonary Dysfunction". The sub-programs have been amalgamated into a Program-Project Grant to formalize an ongoing collaborative effort by investigators whose interests cross interdisciplinary and inter-institutional lines, and who have now expanded activities in shared facilities, added new professional personnel, and increased joint utilization of specific local resources. The overall goal is continuation of a broad, stable, and innovative program of cardiopulmonary research.